1. Field of the Invention
This invention relates generally to compression tools, and more particularly to an improved dental compression apparatus for generating compression in the dental porcelain laminate foil technique.
2. Description of Related Art
Invention and use of dental foil compression devices is known in the medical arts such as the porcelain laminate foil technique. FIG. 4 shows a cross-sectional view of a well known, prior art tool for achieving compression of foils against dental models known as dies. Generally, the problem is how to compress a thin metallic foil against a plaster model of a tooth or other dental structure so that the foil is able to be impressed with the surface contour and roughness of the dental structure. In a later step in the process, the foil will be used as a base for building up a thin porcelain cap or other structure to be fitted over a tooth of a patient. Therefore, the foil must be energetically impressed on the model so as to capture its surface contour with fidelity. The apparatus shown in FIG. 4 is used to achieve such a result. A base portion 50 is a cylindrical fixture having a cavity machined within it. Inside the cavity is placed a dental model holder 30 with the model 60 within it. This is placed over a washer 40 at the bottom of the cavity. A viscous material such as a clay 20 is pressed into the cavity over the dental model 60. A pin 240 extending from the model 60 is used to position the model 60 at the center of the fixture, the pin being positioned within a hole 90 in the washer 40. Further viscous material 20 is pressed into a small cavity in a ram rod 10. The ram rod 10 is then forced into the base portion 50 driving the viscous material 20 into compression and thereby driving the foil against the tooth of the model 60. One major problem with this approach is that the ram rod 10, because it enters the base portion, often damages the model 60. Another problem with this prior art approach is that when the ram rod 10 is removed from the base portion 50, it is not possible to easily remove the model 60. In order to facilitate its removal, a push rod 70 is usually provided. This rod 70 fits within a small diameter hole 80 in the base portion 50 and is able to push against the washer 40, dental model holder 30, model 60 and viscous material 20 to try to dislodge this entire group of items together. However, the washer 40 often tends to bind within the base portion 50 so that it is difficult to remove the model 60. Even when the group is dislodged from the base portion 50, it is not easy to remove the model, in that when the washer 40 has been separated from the dental model holder 30, the model is not easily grasped since it is embedded in the viscous material and is held tightly inside the holder 30. The sharp pin 240 (see FIG. 3) makes this approach to removal of the model even more difficult and problematic. There is a need for a more suitable fixture for accomplishing the same result as the prior art device of FIG. 4 but which is less complex, less expensive to fabricate, and which is easier to load and unload.
The present invention fulfills these needs and provides further related advantages as described in the following summary.